INCONNU/NOT KNOWN/ONBEKEND applied PIETERMARITZBURG, Transvaal postal history with POLISH AIR FORCE boxed on GB KG6 1d cover from Blackpool 18 NO 42 with purple jusqu'a bars denoting insufficient for airmail, on arrival pmk'd 25 II 43/15 and 13 III 43/41 with 4 MAY 1943 return arrival backstamp, some peripheral faults. £95